Bolt, High strength bolts, Screw
Bolts made of high-strength steel or bolts that require significant preload can be referred to as high-strength bolts. High strength bolts are mainly used to connect bridges, tracks, high-voltage and ultra-high-voltage equipment. The fracture of this type of bolt is mainly brittle fracture. High strength bolts used for ultra-high pressure equipment require significant prestressing to ensure the sealing of the container. The bolted connection of the main components of building structures generally adopts high-strength bolts. Ordinary bolts can be reused, while high-strength bolts cannot be reused. High strength bolts are usually used for permanent connections. High strength bolts are pre-stressed bolts. Apply the specified pre-stress with a torque wrench for friction type, and unscrew the plum blossom head for pressure type. Ordinary bolts have poor shear resistance and can be used in secondary structural parts. Ordinary bolts only need to be tightened. Ordinary bolts are generally classified as Grade 4.4, 4.8, 5.6, and 8.8. High strength bolts are generally grade 8.8 and 10.9, with grade 10.9 being the most common. The 8.8 level is the same as the 8.8S level. The stress performance and calculation method of ordinary bolts and high-strength bolts are different. The stress of high-strength bolts is first borne by applying a pre tension force P inside them, and then generating frictional resistance on the contact surface between connectors to withstand external loads, while ordinary bolts directly bear external loads.
